Crushers are used in mining operations to reduce the size of the mined material. In one example of a mining operation (FIG. 30), mined material 1 is dumped into a chute 3 and directed onto a conveyor 5 for transport to a roll crusher 7. The roll crusher 7 in this example is a double roll crusher, which includes a pair of opposed rolls 9 to break up the mined material 1. Each roll 9 is fitted with an array of tips 11 adapted to engage the mined material and break it up (FIG. 31). The tips are secured to bases or holders 13 that are fixed to the rolls 9. The rolls 9 are rotated in opposite directions so that the tips 11 are driven toward each other from the top. The broken material 1A passing through the roll crusher 7 is deposited on a second conveyor 17 for transport to rotary screens 19 for separation of the material.
In a conventional machine, tip 11 is a one-piece member that includes a mounting shaft 21 for attachment to a holder 13, and a cone 23 for engaging the mined material 1 (FIGS. 32-34). Mounting shaft 21 is machined to fit into a machined bore 24 in base 13 to retain the tip in the base, properly orient the tip, and provide sufficient support during use. The use of a machined bore and shaft, however, leads to increased manufacturing costs. Further, fines commonly get embedded in the bore around the shaft during use, which can make the tip difficult to remove from the base.
Further, cone 23 and base 13 suffer considerable abuse and wear during use. Because of the severity of the crushing operation, the tips and bases need regular replacement even with hardfacing and proper maintenance. Moreover, even though only the cone of the tip may be worn out, the entire tip must be replaced. Likewise, even though only the top of the base may be worn out due to the greater exposure during use, the entire base must be replaced. The construction results in a considerable amount of throw-away material. In addition, replacing the tips 11 and/or bases 13 requires substantial time, which results in considerable downtime for the machine.
US Patent Application Publication No. 2009/0174252 discloses a two-piece tip having a machined mounting shaft for receipt into the machined bore in the base, and a wear cap that fits over a seat formed on the front end of the shaft. The wear cap bears the brunt of the crushing operation and protects the underlying seat and mounting shaft. Accordingly, only the wear cap usually needs to be replaced. This is an easy and quick process, and results in considerably less throw-away material as the mounting shaft can be reused. Nevertheless, this system still requires machining of the tip's mounting shaft and the base's bore, and difficulty in removing the mounting shaft from the base on account of fines in the bore. The assembly also still suffers from frequent replacement of the bases, which is a lengthy process and results in considerable throw-away material.